FIG. 1A is a circuit diagram illustrating a prior art CMOS driver for inductive loads. As illustrated in FIG. 1A, a Metal Oxide Semiconductor (MOS) transistor device M1 110 has a gate coupled to an input signal 105 and a drain coupled to an inductive load L 120.
In the circuit shown in FIG. 1A, and as illustrated in the graph of FIG. 1B, at a predetermined time t0, when the input signal 105 goes to zero and the MOS transistor device 110 is turned off, the voltage at the output VOUT and the drain-to-gate voltage VDG at the transistor device M1 110 increase abruptly above the supply voltage VDD, thus reducing the reliability of the device. Among the various contemplated solutions to improve the reliability of the device by keeping the drain-to-gate voltage VDG always lower than the supply voltage VDD, FIG. 2A shows a circuit diagram, wherein two Metal Oxide Semiconductor (MOS) transistor devices M1 210 and M2 220 are coupled in series, with the drain of transistor device M2 220 coupled to an inductive load 250. The gate of transistor device M2 220 is always coupled to the supply voltage VDD, while the gate of transistor device M1 210 receives an input signal IN1 201. FIG. 2A illustrates a half bridge circuit, thus corresponding transistor devices M3 230 and M4 240 are coupled in series such that the gate of transistor device 240 receives an inverse input signal −IN2 202 and the gate of transistor device M3 230 is grounded. In the circuit shown in FIG. 2A and, as illustrated in the graph of FIG. 2B, when the input signal −IN2 goes high and the transistor device M4 240 is turned off, the output voltage VOUT goes below ground and, thus, the drain-to-gate voltage VDG2 at the transistor device M2 220 is greater than the supply voltage VDD, thus reducing the reliability of the device. Similarly, when the input signal IN1 goes low and the transistor M1 210 is turned off, the output voltage goes above VDD and, thus, the drain-to-gate voltage at the transistor device M3 230 is greater than the supply voltage VDD, again affecting the reliability of the device.